They then applied this method to the magnitude 7.9 earthquake that struck the Gulf of Alaska near Kodiak Island on January 23, 2018.Īs study co-author Professor Yuji Yagi explains, "Our method uses a flexible finite-fault inversion framework with improved smoothness constraints. In a new study published in Scientific Reports, a research team led by the University of Tsukuba developed a new method to model the details of complex earthquake rupture processes affecting systems of multiple faults. Of course, given the complexity of the environments where these ruptures typically occur, the reality is often much more complicated. Tsukuba, Japan - An earthquake is generally viewed to be caused by a rupture along a fault that is transmitted outward from its point of origin in a uniform, predictable pattern. The dashed rectangles highlight the rupture events recognised by this study. Lower-right panel shows the spatiotemporal distribution of the slip migration, projected along the north-south direction. Blue lines are our estimate of the faults, along with the fault movements indicated as arrows. Lower-left panel show the enlarged map of our result. Upper panels summarise the regional map of the study area, showing plate boundary (dashed line), seafloor fracture zones (solid lines), the epicentre (star) of the 2018 Gulf of Alaska earthquake and the aftershocks (dots). ![]() The maximum horizontal compressive stress is nearly normal to the trace of the Denali fault and rotates gradually from NW orientation at the western end of the rupture zone to NE orientation near the junction with the Totschunda fault.Image: Summary of study area and result. The stress orientations before and after the event are nearly identical. We calculated principal stress directions along the Denali fault both before and after the 7.9 event from the focal mechanisms. The aftershocks are located not only along the main rupture zone, but also illuminate multiple splay faults north and south of the Denali fault. The relocated aftershocks indicate complex faulting along the rupture zone. We used the double difference method to relocate aftershocks of both the 6.7 and 7.9 events. In this presentation, we will present and interpret the aftershock location patterns, first motion focal mechanism solutions, and regional seismic moment tensors for the larger events. After the event, the processing load increased to over 300 events per day during the first week following the event. Prior to the 7.9 Denali Fault event, the AEIC was locating 35 to 50 events per day. The AEIC staff installed a temporary seismic network of 6 instruments following the 6.7 earthquake and an additional 20 stations following the 7.9 earthquake. The data from these stations are collected, processed and archived at the AEIC. The rest of the stations are either 1 or 3-component short-period instruments. Nearly 40 of these sites are equipped with the broad-band sensors, some of which also have strong motion sensors. The AEIC acquires and processes data from the Alaska Seismic Network, consisting of over 350 seismograph stations. The earthquakes were recorded and processed by the Alaska Earthquake Information Center (AEIC). The cumulative length of the 6.7 and 7.9 aftershock zones along the Denali and Totschunda faults is about 380 km. At about 143W the rupture moved onto the adjacent southeast-trending Totschunda fault and propagated for another 55 km. Then the rupture transferred to the Denali fault and propagated eastward for 220 km. ![]() The rupture began on the northeast trending Susitna Glacier Thrust fault, a splay fault south of the Denali fault. The 7.9 event ruptured three different faults. The geologists mapped a ~300-km-long rupture and measured maximum offsets of 8.8 meters. Aftershock locations and surface slip observations from the 7.9 quake indicate that the rupture was predominately unilateral in the eastward direction. This earlier earthquake and its zone of aftershocks were located ~20 km to the west of the 7.9 quake. It was preceded by a magnitude 6.7 earthquake on October 23. The largest earthquake ever recorded on the Denali fault system (magnitude 7.9) struck central Alaska on November 3, 2002.
0 Comments
Leave a Reply. |
Details
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |